Electrical system compatibility

[XSLeo]

On the TCI ignition you need battery power to both the TCI box and coil. From your kill switch a r/w wire feeds power to the coil and the TCI box.
Ok a quick run down on how the TCI works. As the engine turns over a magnet in the alternator rotor passes the pick coil. This triggers the pick ups to send a signal to the TCI box. The TCI box uses this signal to know when to spark the coil.
The coil gets power on the r/w wire, This power flows through the coil and out the orange wire to the TCI box. The TCI box uses a transistor to ground the coil. When the TCI box wants spark it ungrounds the coil.
It works about like points only uses a transistor instead of points.
So without powr to both the TCI box and coil, no spark.
When testing for spark both plugs need to be used. As the coil fires, the spark current flows out one coil wire to a plug, jumps the plug gap to spark, then goes into the head, across to the other plug jumps the gap to spark that plug, then up the plug wire back to the coil to complete the circuit. So to test for spark one plug wire must be on a plug in the engine with the plug wire hooked up. Then hold the other plug to head.
Some of us have built a plug tester by using a wire, like the bare solid ground wire out of some house wiring. A piece about 18 inches long. Twist one end around a plug, snug enough to hold the plug yet let you screw the plug in/out. Do this to both ends. Slip this wire in across the top of engine, screw in both plugs, hook plug wires, test for spark. Both should have a good spark.
Leo

 

[Prisondawg]

On the TCI ignition you need battery power to both the TCI box and coil. From your kill switch a r/w wire feeds power to the coil and the TCI box.
Ok a quick run down on how the TCI works. As the engine turns over a magnet in the alternator rotor passes the pick coil. This triggers the pick ups to send a signal to the TCI box. The TCI box uses this signal to know when to spark the coil.
The coil gets power on the r/w wire, This power flows through the coil and out the orange wire to the TCI box. The TCI box uses a transistor to ground the coil. When the TCI box wants spark it ungrounds the coil.
It works about like points only uses a transistor instead of points.
So without powr to both the TCI box and coil, no spark.
When testing for spark both plugs need to be used. As the coil fires, the spark current flows out one coil wire to a plug, jumps the plug gap to spark, then goes into the head, across to the other plug jumps the gap to spark that plug, then up the plug wire back to the coil to complete the circuit. So to test for spark one plug wire must be on a plug in the engine with the plug wire hooked up. Then hold the other plug to head.
Some of us have built a plug tester by using a wire, like the bare solid ground wire out of some house wiring. A piece about 18 inches long. Twist one end around a plug, snug enough to hold the plug yet let you screw the plug in/out. Do this to both ends. Slip this wire in across the top of engine, screw in both plugs, hook plug wires, test for spark. Both should have a good spark.
Leo

Great write up, Leo. I just ordered a new coil from Mike's xs, as well as spark plugs wires and spark plugs, and even a spark plugs tester. I'm going to hook all that up, and make sure the tci box has power, and if I still don't have spark, im going to assume the TCI box I have is bad. I read in a different post that its possible to repair a TCI box by replacing the old transistors. But I ALSO have read bia my clymer manual that the TCI box is unrepairable

 

[Prisondawg]

I fear the TCI box I have is burnt out, are there any reliable new reproductions that don't cost an arm and a leg? Or should I just keep checking eBay for a working used one ?

 

[Prisondawg]

Ok, I have done it. I have spark, my head lights and turn signals work. I even got the bike to turn over for a little bit. But my problems are no longer electrical. A summary of the issue: using a 76 wiring harness on an 82 engine. The 82 engine uses a transisterized timing vs the points used in the 76 therefore new pieces were introduced that were not present in the 76. Those pieces are:

Single coil (instead of dual coil)

Solid state / regulator rectifier ( rather than the regulator and rectifier being separate)

TCI ignition box (rather than points)

These items had to be incorporated into the wiring harness of the 76. To do that I used simplified wiring diagrams from here, and the wiring diagram from my repair manual. On my engine the wires were cut so I had to replace them with new terminal connectors, which I ordered from mikes XS. I have to say after trying to get my electrical system working for weeks. Seeing the headlights turn on and my spark plug spark was pretty exhilarating. I couldn’t have done it without the help from everyone in this thread, thank you. It’s all mechanical from here out. I’m sure I’ll be flooding the feeds with questions about that soon.

 

[Prisondawg]